Respiratory symptoms, airway inflammation and lung function in workers at risk of occupational asthma

Background: Fractional exhaled nitric oxide (FENO) is increasingly used in asthma, but its role in occupational asthma (OA) is not established. Aim: To explore relationships between FENO and symptoms, asthma, and lung function in wood, foundry, and laboratory animal workers. Method: Workers underwent validated questionnaire, FENO, and spirometry measured to ATS/ERS standards. Associations were examined between FENO >40ppb and work-related respiratory symptoms (WRRS); and between current asthma symptoms (CAS) and either FENO >40ppb, or CAS and FEV1 below the lower limit of normal (LLN). Degree of overlap between workers with FENO >40ppb, FEV1 Results: In total 655 workers took part. Mean age was 39 (SD 12.5) years, 86% were male and 25% current smokers. Overall 40% of workers reported CAS and 20% had elevated FENO. FENO >40ppb was associated with asthma (OR for FENO >40 ppb 2.12, 95% CI 1.19 – 3.78). Nine per cent of workers had both CAS and high FENO: the risk of WRRS was elevated in this group (OR 3.75, 2.01 – 7.00). No increased risk of WRRS was seen in workers with CAS and obstructive spirometry. Among workers with CAS, little overlap existed between those with high FENO and those with low FEV1. Over half those with CAS and high FENO had no previous asthma diagnosis. Conclusion: CAS were common among workers exposed to a range of known occupational allergens. Measurement of FENO in the workplace can be used to help identify symptomatic workers with eosinophilic airway inflammation. A significant proportion of these workers have never been diagnosed with asthma, suggesting there may be a role for FENO in health surveillance for OA.